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PRECISION MEASUREMENTS OF DEUTERON PHOTODISINTEGRATION USING LINEARLY POLARIZED PHOTONS OF 14 AND 16 MEV

by Blackston, Matthew Allen

Abstract (Summary)
A precision measurement of the d(gamma

,n)p reaction was performed at the High

Intensity

gamma-ray Source (HIGS), which is located at the Duke Free Electron Laser

Laboratory on the campus of Duke University. The

gamma-ray beams were nearly 100%

linearly polarized, allowing the angular distributions of both the analyzing power

and unpolarized cross section to be measured at 14 and 16 MeV. The photons were

incident on a heavy water target and the neutrons from the photodisintegration

reaction were detected using the Blowfish detector array, which consists of 88 liquid

scintillator detectors with large angular coverage.A transition matrix element (TME) analysis was performed on the data which

allowed the amplitudes of the TMEs which contribute to the reaction at these energies

to be extracted. This was done by invoking Watson's theorem, which fixes the relative

TME phases using the n-p scattering phase shifts, leaving the TME amplitudes as

free parameters in fits to the data. The results indicated very good agreement with

a recent potential model calculation for the amplitudes of the three electric dipole

(E1) p-waves, which account for over 90% of the cross section at these energies.The extracted TME amplitudes were then used to construct the observable which

enters into the Gerasimov-Drell-Hearn (GDH) Sum Rule integrand. The results are

the first experimental indication of a positive value of the GDH integrand in the

region near photodisintegration threshold. A positive value at these energies has

been shown by theory to be due to relativistic contributions.

Bibliographical Information:

Advisor:Weller, Henry R

School:Duke University

School Location:USA - North Carolina

Source Type:Master's Thesis

Keywords:physics nuclear photodisintegration deuteron gamma rays polarized gdh sum rule

ISBN:

Date of Publication:07/27/2007

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